1. Field of the Invention
The present invention relates generally to a series fan, and more particularly to a series fan having higher support strength and protection effect. Moreover, the dynamic blades can be designed with an increased aerodynamic volume.
2. Description of the Related Art
Along with the advance of sciences and technologies, the reliance of peoples on various electronic apparatuses has more and more increased. In operation, the internal components of the electronic products (such as computers and laptops) will generate high heat. The heat must be dissipated to outer side of the electronic products in time. Otherwise, the problem of overheating will take place. Therefore, most of the electronic products are provided with fans disposed therein for actively dissipating the heat and keeping the electronic products working at an operation temperature within a range. In some cases, the air volume provided by one single fan may be insufficient. Under such circumstance, two or more fans are often serially connected and assembled and co-used to provide sufficient air volume.
Please refer to FIG. 1. A conventional series fan 4 includes anterior dynamic blades 41, anterior static blades 42, posterior static blades 43 and posterior dynamic blades 44, which are sequentially arranged from air inlet to air outlet. The anterior static blades 42 and posterior static blades 43 are the main support members for the series fan 4. However, the anterior static blades 42 and posterior static blades 43 are disposed at the middle of the series fan 4. Therefore, the positions where the anterior dynamic blades 41 and the posterior dynamic blades 44 are positioned will have a relatively weak structural strength and support. That is, the structural support for the air inlet and air outlet of the series fan 4 is relatively weak. Moreover, in general, when the series fan 4 is fixed on an electronic device, the air inlet or the air outlet is assembled with the electronic device. The anterior dynamic blades 41 and the posterior dynamic blades 44 are positioned at the air inlet and the air outlet and have relatively weak structural support. Therefore, the total vibration value of the series fan 4 is increased. This will affect the systematic stability of the entire series fan. Also, the anterior dynamic blades 41 and the posterior dynamic blades 44 are positioned at the air inlet and the air outlet in an open state. In consideration of security, it is necessary to add protection screens to the air inlet and air outlet. Under such circumstance, the airflow is obstructed and the material cost is increased. Also, the working time is prolonged.
Furthermore, when the conventional series fan 4 is mounted in the electronic device, the assembling height is limited to a fixed height. Therefore, the total thickness of the series fan is also limited. However, the anterior static blades 42 and posterior static blades 43 are the main support members for the series fan 4. However, the anterior dynamic blades 41, the anterior static blades 42, the posterior static blades 43 and the posterior dynamic blades 44 are arranged in fixed positions. Therefore, the anterior static blades 42 and the posterior static blades 43 are located in fixed relationship to each other. In this case, the allowable arrangement thickness of the anterior dynamic blades 41 and the posterior dynamic blades 44 is limited. As a result, it is impossible to enhance the aerodynamic design of the anterior dynamic blades 41 and the posterior dynamic blades 44. According to the above, the conventional series fan has the following shortcomings:    1. The total vibration value is increased.    2. The material cost is increased and the working time is prolonged.    3. It is impossible to enhance the aerodynamic design of the anterior dynamic blades and the posterior dynamic blades.